1. Field of the Invention
The present invention relates to a tapered roller bearing.
2. Description of the Related Art
A tapered roller bearing is characterized to have a larger load capacity and a higher rigidity than other rolling bearings of the same size. FIG. 8 is a longitudinal sectional view depicting a conventional tapered roller bearing 100. The tapered roller bearing 100 includes an inner ring 101, an outer ring 102, a plurality of tapered rollers 103, and an annular cage 104 (see, for example, Japanese Patent Application Publication No. 2013-221592 (JP 2013-221592 A). The cage 104 holds the tapered rollers 103 spaced at intervals in a circumferential direction.
The cage 104 has a small-diameter annular portion 105 on a first side in an axial direction (the left side in FIG. 8), a large-diameter annular portion 106 on a second side in the axial direction (the right side in FIG. 8), and a plurality of cage bar portions 107. The cage bar portions 107 couple the annular portions 105 and 106 together. Each space formed between the annular portions 105 and 106 and between the cage bar portions 107 and 107 that are adjacent in a circumferential direction serves as a pocket 108 in which the corresponding tapered rollers 103 is housed.
In the tapered roller bearing 100 (the invention described in JP 2013-221592 A), the small-diameter annular portion 105 has an increased thickness dimension (radial dimension) to restrain lubricant from entering a bearing interior through an annular opening 109 between the inner ring 101 and the outer ring 102. This enables a reduction in stirring resistance of the lubricant inside the bearing.
Assembly of the tapered roller bearing 100 as depicted in FIG. 8 can be performed as described below. First, the tapered rollers 103 are housed in the respective pockets 108 of the cage 104. The cage bar portions 107 of the cage 104 inhibit the tapered rollers 103 housed in the pockets 108 from falling outward in a radial direction. With the tapered rollers 103 held in the cage 104 (pockets 108), the inner ring 101 is moved closer to the tapered rollers 103 along the axial direction. The tapered rollers 103 are positioned on an inner-ring raceway surface 101a of the inner ring 101.
After the inner ring 101 starts to be moved closer to the tapered rollers 103 and before the tapered rollers 103 are positioned on the inner-ring raceway surface 101a, small diameter portions 110 of the tapered rollers 103 need to be displaced outward in the radial direction over a cone front face rib (hereinafter referred to as “small rib”) 101b of the inner ring 101. However, the displacement is regulated by the cage bar portions 107. Thus, in the related art, a strong force is exerted on the inner ring 101 by a press or the like to press the inner ring 101 against the cage 104 with the tapered rollers 103 held in the pockets 108. When the small diameter portions 110 pass over the small rib 101b, the cage 104 is elastically deformed (the diameter of the cage 104 is increased) to position the tapered rollers 103 on the inner-ring raceway surface 101a. Thus, an inner ring unit is obtained which includes the inner ring 101, the cage 104, and the tapered rollers 103 integrated together. The outer ring 102 is assembled to the inner ring unit to complete the tapered roller bearing 100.
However, when the small diameter portions 110 of the tapered rollers 103 pass over the small rib 101b of the inner ring 101, an excessive force acts on the cage 104. As a result, the cage 104 may have reduced dimensional accuracy or may be damaged. In other words, assembly of the tapered roller bearing is not easy in which the inner ring 101 is assembled to the cage 104 with the tapered rollers 103 held therein. In particular, in the cage 104 depicted in FIG. 8, the small-diameter annular portion 105 has a large thickness dimension (large radial dimension). Thus, the cage 104 is difficult to elastically deform (the diameter of the cage 104 is difficult to increase), making assembly of the bearing having the cage 104 further difficult.